I would use the (very technical) Speedy Entry Tool dialog box Edit Frame:

(make sure you are in the right layer)
Speedy Entry Tool.
Click outside the staff, to exit the entry rectangle.
Hold down the correct modifier key (Windows: Ctrl; Mac: Option), and click in the staff/measure.

In the dialog Edit Frame, navigate to the relevant entry, and de-select Ledger.

Do you still use Finale 2009 ?
If you now have a more recent version than the one mentioned in your signature (10 years old), you could use the JW Change plug-in -> Note Entries -> Ledger Lines -> Hide (with a layer selected).
If you don't, Peter's suggestion is the way yo go.

Last edited by michelp on Thu Jan 16, 2020 4:36 pm, edited 3 times in total.

I make a lot of lead sheets with "extra" stuff like rhythm notes above/below the staff etc. Sometimes I'd like to hide the ledger lines for the extra stuff and retain them for the main notated melody.

You might consider using an extra staff for the extra stuff . E.g. a staff with no barlines, no staff lines etc. . This staff can have any distance from the main staff and can also have a different size - possibilities which might come in handy.